1. Field of the Invention
The present invention relates generally to the design of a safety restraint system and more particularly to a design methodology and design of experiments system for the design and development of a safety restraint system for an automobile.
2. Description
New government requirements have significantly increased the number of test scenarios under which a safety restraints system must be evaluated. The new rules amend the occupant crash protection standards to require that future air bags be designed to create less risk of serious air bag induced injuries, particularly for small women and young children. Future restraint systems must further provide improved frontal crash protection for all occupants, by means that include advanced air bag technology. To achieve these goals, a wide variety of new requirements have been added including test procedures, injury criteria, and the use of an assortment of new anthropomorphic dummies. These new requirements, coupled with a shortened vehicle development cycle, significantly increase the need for improved design methodologies.
Specific injury criteria for a number of anthropomorphic dummies have been set. More specifically, head injury criteria (HIC), neck injury criteria (including tension, compression and flexion), thoracic criteria (including chest acceleration and chest deflection) and femur axial loads have been set for: hybrid III mid-sized male, hybrid III small female, hybrid III 6-year-old child, hybrid III 3-year-old child, and 12-month-old infant anthropomorphic dummies. For any given injury criteria value, a statistical probability of a particular injury severity can be determined. By using these injury criteria to design a restraints system, it is possible to statistically determine for a given occupant and crash situation what the likelihood of injury will be and therefore evaluate the effectiveness of changes to a restraint system. Prior to the incorporation of the new requirements, manufacturers were required to design air bag systems using the hybrid III mid-sized male. Due to the often complicated nature of these systems and crash events, it is often not possible to design the system for protecting all possible occupants for all possible crash situations.
While the theory of safety restraints design and its applications to various restraint components has advanced considerably in the past decade, the bulk of that knowledge has repeatedly stayed within the laboratory. This has mainly resulted from the obtuse nature of the laboratory-derived knowledge and the requirement that the engineer or technical expert must be integrally involved in applying the theoretical knowledge to a given unexpected crash situation.
Significant advancements have been made in testing methodologies and computer modeling of restraints systems. As is known in the restraints community, small modifications to the output of various restraint components often lead to significant changes in injury responses in occupants in varying crash conditions. As such, changes to the vehicle, as the vehicle progresses through its development, often require that changes be made to the restraints system. Using previous methodologies, this would significantly increase the amount of testing and computer simulations that must be run to verify the response of the system to changes in the vehicle structure. Should the testing show that test results for a given occupant would fall out of acceptable government or vehicle manufacturer specifications, a significant amount of redesign and re-testing would be necessary. Such recursive changes required to bring the system in compliance for one class of occupants can quickly take the response levels far away from acceptable limits for other occupants.
Engineers have performed complex design of experiments to study the interrelationships between automotive safety restraint components and occupant responses. This work has produced mathematical models that are typically very intricate, requiring three-dimensional depictions of the inner relationships (as shown for example in FIG. 1).
The various surfaces of FIG. 1 show exemplary inter-relationships between three crash factors and one occupant response. The crash factors may be the output of an air bag inflator, such as the pressure or temperature, the stiffness of a knee bolster, or a seat belt""s elasticity. The occupant""s response may be an attribute of injury criteria such as chest deflection. FIG. 1 illustrates how changes in the restraint factors affect the occupant""s response. For example, surface 20 shows that parameters of the restraint factors produce a response value of xe2x80x9c30xe2x80x9d. As shown in FIGS. 2a-2b, contour plots can be used to depict inter-relationships between restraint factors and the occupant responses in a two-dimensional view.
To use the experimental results in a restraints system, the contour plots were studied to determine the optimal restraint component factors that would achieve a particular occupant response. To determine the restraint factors needed to achieve a desired level for two occupant responses, the contour plots for two occupant responses were placed atop of each other (see FIG. 2c); thereupon restraint factors were determined based upon the area, of both desired occupant response levels. The difficulty of analyzing the contour plots dramatically increases with the number of occupant restraint factors and responses involved. The new government regulations have significantly increased these occupant restraint factors by increasing the number of crash scenarios and occupants to be tested, making use of contour plots untenable.
The design of experiments approach was then used in the ever-changing vehicle environments. When the restraint factors and responses had to be changed from the tested initial laboratory configuration, the design of experiments determined a set of optimal restraint factors. The unwieldy manner of the contour plots to effectively address the ever-changing restraint factors and responses within a vehicle""s restraint system development, hindered the ability of design of experiments to assist in modifying the restraint factors. Accordingly, modifications to the restraint factors within the design and development of a restraints system to achieve the desired occupant responses was an art form. This art form was to be learned from years of experience in controlling the restraint equipment within a vehicle. Due to these reasons, the development of a restraints system lacks the effective use of the design of experiments approach for controlling a restraints system, especially in view of the reduced cycle time needed in the development of an automobile.
As such, a computer implemented method for designing a safety restraints system so that a predetermined desired level of occupant responses is produced is disclosed. This method includes the steps of storing an occupant restraint factor response model in a computer storage media. The model relates at least one predetermined restraint factor having a level, which is indicative of an output for components within the design of the restraint system, with an occupant""s response. The methodology determines the level of an occupant""s response based upon the model and upon a first level of restraint factors. The model then determines a second level of the restraint factors, which produce the desired level of the occupant""s response based upon the determined level of restraint factors. In addition, the system modifies the restraints system based upon the determined second level of the restraint factors, which produces the desired level of the occupant response. This modification utilizes optimization techniques such as a simplex methodology.
Further disclosed is a computer-implemented method for controlling the design of an occupant restraints system so that a predetermined desired level of occupant responses is produced, the system having the steps of: storing an occupant restraint factor response model in a computer storage media. The model relates at least one predetermined restraint factor with the occupant response, the restraint factors having a level that is indicative of setting various values for controlling the design of the restraints system. Next, the system establishes at least one constant for the model, based upon the desired value of the vehicle occupant""s response. Next, the system determines the level of the restraint factors, which produce the desired level of restraint response, based upon the model having the established constraint. Finally, the system controls the design of the occupant restraint system based upon the determined level of the restraint factors, which produce the desired level of the occupant""s response.
Further disclosed is a safety restraint design controller for controlling the design of a safety restraints system so that a predetermined desired level of occupant""s response is produced. The controller has a database for storing an expert restraint factor response model, the model interrelating at least one predetermined restraint factor with the occupant response, the restraint factor having a level which is indicative of setting values for controlling the safety restraint design. A database engine is connected to the database for determining a level for the occupant response based upon the model and upon the first level restraint factors. In addition, an optimizer is connected to the database engine for determining a second level of the restraint factors, which produce the desired level of the occupant response based upon the desired level of the occupant response from the database engine. Whereby the safety restraint""s design is controlled based upon the determined second level of the restraint factors, which produce the desired level of the safety response.
Further disclosed is a system design methodology, which is broken into four general stages: pre-design verification; design verification; pre-product validation; and product validation. Each of these stages incorporates vehicle crashes, sled testing, numerical analysis, and sensor development. The preferred proposed development methodology requires 5 (five) crash test phases, 7 (seven) sled test phases, and 4 (four) out-of-position occupant option phases. Extensive computer simulation is conducted between the general stages using a design of experiments method. Each of the design of experiments produces polynomial equations that can be used to calculate all of the occupant responses for every test condition. A complete fire/no fire matrix is generated from the design of experiments after each phase of simulation. A biomechanical algorithm is developed based on the design of experiments and the fire/no fire matrix. The restraint factors and occupant responses from each phase of the vehicle crashes and sled tests are used to confirm the accuracy and tune the polynomial equations and the fire/no fire matrix.
Further disclosed is a method of providing and selecting from a menu on the display in a restraints controller. The method includes retrieving a set of menu entries for a menu, each menu entry representing an occupant restraint characteristic. The set of menu display options is displayed, on a display; where the controller receives a menu entry selection signal indicative of the selection device pointing at a selected menu entry from the set menu entries. In response to the signal, the controller performs a search of a database for injury data corresponding to the occupant response represented by the selected menu entry.